The invention concerns an apparatus for the production of glass mat reinforced thermoplastic materials.
Apparatuses of this type are known from German Pat. No. OS-23 12 816. In the known configurations two reinforcing fibers mats are introduced separately in the form of webs into a gap between two feed rolls, and an extruded strand of a thermoplastic resin is sandwiched between the two fiber mats. This sandwich enters a compression zone, wherein the resin penetrates the fiber mats under the effect of (a) heating the fiber mats as well as the rolls transporting them in the compression zone, and (b) the pressure in the compression zone generated by two revolving endless belts. Then, the sandwich is passed through a cooling zone to form the desired end product. The feeding of the extruded material is not easily controlled and much care must be taken in the known process and apparatus to ensure that the resin introduced between the glass fiber mats actually penetrates the mats, so that the finished product will have a smooth outer surface.
It is also known to use for the production of a glass fiber reinforced thermoplastic resin plate a so-called twin belt press, for example as disclosed by German Pat. No. 29 48 235, into the press gap of which are introduced two glass fiber mats with an extruded resin strand disposed between the mats. On the outside of each mat is disposed a film of a thermoplastic resin. This apparatus has, however, the disadvantage that if the films comprise prefabricated foil sheets, additional heat must be applied in the compression zone. Also, the thickness of the prefabricated film does not make possible any adaptation or conversion of the outside surfaces of the plates to another grade.
It is an object of the present invention to make possible the accurately metered feeding of thermoplastic resin, whereby the desired impregnation of the glass fiber mats and the satisfactory formation of the outside surfaces of the finished product are assured.